linux-stable.git/arch/arm/boot/compressed/misc.c, branch linux-4.2.y

stackprotector: Introduce CONFIG_CC_STACKPROTECTOR_STRONG

2013-12-20T08:38:40+00:00

This changes the stack protector config option into a choice of
"None", "Regular", and "Strong":

   CONFIG_CC_STACKPROTECTOR_NONE
   CONFIG_CC_STACKPROTECTOR_REGULAR
   CONFIG_CC_STACKPROTECTOR_STRONG

"Regular" means the old CONFIG_CC_STACKPROTECTOR=y option.

"Strong" is a new mode introduced by this patch. With "Strong" the
kernel is built with -fstack-protector-strong (available in
gcc 4.9 and later). This option increases the coverage of the stack
protector without the heavy performance hit of -fstack-protector-all.

For reference, the stack protector options available in gcc are:

-fstack-protector-all:
  Adds the stack-canary saving prefix and stack-canary checking
  suffix to _all_ function entry and exit. Results in substantial
  use of stack space for saving the canary for deep stack users
  (e.g. historically xfs), and measurable (though shockingly still
  low) performance hit due to all the saving/checking. Really not
  suitable for sane systems, and was entirely removed as an option
  from the kernel many years ago.

-fstack-protector:
  Adds the canary save/check to functions that define an 8
  (--param=ssp-buffer-size=N, N=8 by default) or more byte local
  char array. Traditionally, stack overflows happened with
  string-based manipulations, so this was a way to find those
  functions. Very few total functions actually get the canary; no
  measurable performance or size overhead.

-fstack-protector-strong
  Adds the canary for a wider set of functions, since it's not
  just those with strings that have ultimately been vulnerable to
  stack-busting. With this superset, more functions end up with a
  canary, but it still remains small compared to all functions
  with only a small change in performance. Based on the original
  design document, a function gets the canary when it contains any
  of:

    - local variable's address used as part of the right hand side
      of an assignment or function argument
    - local variable is an array (or union containing an array),
      regardless of array type or length
    - uses register local variables

  https://docs.google.com/a/google.com/document/d/1xXBH6rRZue4f296vGt9YQcuLVQHeE516stHwt8M9xyU

Find below a comparison of "size" and "objdump" output when built with
gcc-4.9 in three configurations:

  - defconfig
	11430641 kernel text size
	36110 function bodies

  - defconfig + CONFIG_CC_STACKPROTECTOR_REGULAR
	11468490 kernel text size (+0.33%)
	1015 of 36110 functions are stack-protected (2.81%)

  - defconfig + CONFIG_CC_STACKPROTECTOR_STRONG via this patch
	11692790 kernel text size (+2.24%)
	7401 of 36110 functions are stack-protected (20.5%)

With -strong, ARM's compressed boot code now triggers stack
protection, so a static guard was added. Since this is only used
during decompression and was never used before, the exposure
here is very small. Once it switches to the full kernel, the
stack guard is back to normal.

Chrome OS has been using -fstack-protector-strong for its kernel
builds for the last 8 months with no problems.

Signed-off-by: Kees Cook 
Cc: Arjan van de Ven 
Cc: Michal Marek 
Cc: Russell King 
Cc: Ralf Baechle 
Cc: Paul Mundt 
Cc: James Hogan 
Cc: Stephen Rothwell 
Cc: Shawn Guo 
Cc: Linus Torvalds 
Cc: Andrew Morton 
Cc: Peter Zijlstra 
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-mips@linux-mips.org
Cc: linux-arch@vger.kernel.org
Link: http://lkml.kernel.org/r/1387481759-14535-3-git-send-email-keescook@chromium.org
[ Improved the changelog and descriptions some more. ]
Signed-off-by: Ingo Molnar

ARM: 7671/1: use Kconfig to select uncompress.h

2013-03-15T17:18:51+00:00

Following the approach handling DEBUG_LL inclusion, the patch creates
a Kconfig symbol CONFIG_UNCOMPRESS_INCLUDE for choosing the correct
uncompress header.  For traditional build, mach/uncompress.h will be
included in arch/arm/boot/compressed/misc.c.  For multiplatform build,
debug/uncompress.h which contains a suite of empty functions will be
used.  In this way, a platform with particular uncompress.h
implementation could choose its own uncompress.h with this Kconfig
option.

Signed-off-by: Shawn Guo 
Signed-off-by: Russell King

ARM: initial multiplatform support

2012-09-14T14:22:06+00:00

This lets us build a multiplatform kernel for experimental purposes.
However, it will not be useful for any real work, because it relies
on a number of useful things to be disabled for now:

* SMP support must be turned off because of conflicting symbols.
  Marc Zyngier has proposed a solution by adding a new SOC
  operations structure to hold indirect function pointers
  for these, but that work is currently stalled

* We turn on SPARSE_IRQ unconditionally, which is not supported
  on most platforms. Each of them is currently in a different
  state, but most are being worked on.

* A common clock framework is in place since v3.4 but not yet
  being used. Work on this is on its way.

* DEBUG_LL for early debugging is currently disabled.

* THUMB2_KERNEL does not work with allyesconfig because the
  kernel gets too big

[Rob Herring]: Rebased to not be dependent on the mass mach header rename.
As a result, omap2plus, imx, mxs and ux500 are not converted. Highbank,
picoxcell, mvebu, and socfpga are converted.

Signed-off-by: Arnd Bergmann 
Signed-off-by: Rob Herring 
Cc: Russell King 
Cc: Jason Cooper 
Cc: Andrew Lunn 
Acked-by: Jamie Iles 
Cc: Dinh Nguyen

ARM: zImage: gather some string functions into string.c

2011-09-14T17:51:58+00:00

This is a small subset of string functions needed by commits to come.
Except for memcpy() which is unchanged from its original location, their
implementation is meant to be small, and -Os is enforced to prevent gcc
from doing pointless loop unrolling.

Signed-off-by: Nicolas Pitre 
Tested-by: Shawn Guo 
Tested-by: Dave Martin 
Tested-by: Thomas Abraham

Merge branch 'zImage_fixes' of git://git.linaro.org/people/nico/linux into devel-stable

2011-05-07T07:34:02+00:00

ARM: zImage: don't ignore error returned from decompress()

2011-05-07T04:08:01+00:00

If decompress() returns an error without calling error(), we must
not attempt to boot the resulting kernel.

Signed-off-by: Nicolas Pitre 
Tested-by: Shawn Guo 
Tested-by: Tony Lindgren

ARM: zImage: simplify decompress_kernel()

2011-05-07T04:08:00+00:00

The return value for decompress_kernel() is no longer used.  Furthermore,
this was obtained and stored in a variable called output_ptr which is
a complete misnomer for what is actually the size of the decompressed
kernel image.  Let's get rid of it.

Signed-off-by: Nicolas Pitre 
Tested-by: Shawn Guo 
Tested-by: Tony Lindgren

ARM: 6826/1: Merge v6 and v7 DEBUG_LL DCC support

2011-03-28T18:01:43+00:00

The inline assembly differences for v6 vs. v7 are purely
optimizations. On a v7 processor, an mrc with the pc sets the
condition codes to the 28-31 bits of the register being read. It
just so happens that the TX/RX full bits the DCC support code is
testing for are high enough in the register to be put into the
condition codes. On a v6 processor, this "feature" isn't
implemented and thus we have to do the usual read, mask, test
operations to check for TX/RX full. Thus, we can drop the v7
implementation and just use the v6 implementation for both.

Cc: Tony Lindgren 
Signed-off-by: Stephen Boyd 
Signed-off-by: Russell King

ARM: v6k: introduce CPU_V6K option

2011-02-02T21:23:26+00:00

Introduce a CPU_V6K configuration option for platforms to select if they
have a V6K CPU core.  This allows us to identify whether we need to
support ARMv6 CPUs without the V6K SMP extensions at build time.

Currently CPU_V6K is just an alias for CPU_V6, and all places which
reference CPU_V6 are replaced by (CPU_V6 || CPU_V6K).

Select CPU_V6K from platforms which are known to be V6K-only.

Acked-by: Tony Lindgren 
Tested-by: Sourav Poddar 
Tested-by: Will Deacon 
Signed-off-by: Russell King

ARM: remove bit-rotten STANDALONE_DEBUG for decompressor

2010-07-07T14:38:16+00:00

I tried to get this running to debug the regression introduced by
e7db7b4 without success.  But this has several problems that make it
hard to fix:

  - lib/decompress_inflate.c includes in-kernel headers that make
    it difficult to compile for user space.
  - the binary formats changed both in kernel and user space and
    at least for the kernel side there isn't only a single
    variant.

Signed-off-by: Uwe Kleine-König 
Acked-by: Nicolas Pitre